Shear Bond Strength of New and Recycled

Braz Dent J (2006) 17(1): 44-48 44

S.W. Tavares et al.

ISSN 0103-6440

Shear Bond Strength of New and Recycled Brackets to Enamel Stenyo Wanderley TAVARES1 Simonides CONSANI2 Darcy Flávio NOUER1 Maria Beatriz Borges de Araújo MAGNANI1 Paulo Roberto Aranha NOUER3 Laura Moura MARTINS3

1Discipline of Orthodontics;2Discipline of Dental Materials, Faculty of Dentistry of Piracicaba,

State University of Campinas (UNICAMP), Piracicaba, SP, Brazil 3Discipline of Orthodontics and Maxillary Functional Orthopedics,

São Leopoldo Mandic Research Center, Campinas, SP, Brazil

The purpose of this study was to evaluate in vitro the shear bond strength of recycled orthodontic brackets. S2C-03Z brackets (Dental Morelli, Brazil) were bonded to the buccal surfaces of 50 extracted human premolars using Concise Orthodontic chemically cured composite resin (3M, USA). The teeth were randomly assigned to 5 groups (n=10), as follows. In group I (control), the bonded brackets remained attached until shear testing (i.e., no debonding/rebonding). In groups II, III and IV, the bonded brackets were detached and rebonded after recycling by 90-μm particle aluminum oxide blasting, silicon carbide stone grinding or an industrial process at a specialized contractor company (Abzil-Lancer, Brazil), respectively. In group V, the bonded brackets were removed and new brackets were bonded to the enamel surface. Shear bond strength was tested in an Instron machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey’s test at 5% significance level. There was no statistically significant difference (p>0.05) between the control brackets (0.52 kgf/mm2), brackets recycled by aluminum oxide blasting (0.34 kgf/mm2) and new brackets attached to previously bonded teeth (0.43 kgf/mm2). Brackets recycled by the specialized company (0.28 kgf/mm2) and those recycled by silicon carbide stone grinding (0.14 kgf/mm2) showed the lowest shear strength means and differed statistically from control brackets (0.52 kgf/ mm2) (p0.05) between groups I (control), II (airabraded recycled brackets) and V (new brackets bonded to previously bonded teeth). Group IV (industrial recycling) did not differ statistically from groups II and V (p>0.05), but had statistically lower shear bond strength means than group I (control) (p